Special prosecutors should be used in cases of alleged police misconduct, the Rev. Al Sharpton urged Saturday, complaining anew about a New York grand jury's failure to indict officers in the death of Eric Garner while noting a Maryland prosecutor had filed charges against six Baltimore officers in the death of Freddie Gray.

With Garner's family seated silently behind him during his weekly address at the Harlem offices of his National Action Network organization, Sharpton said local prosecutors sometimes bow to local political pressure when deciding whether to file charges in cases of alleged police misconduct.

"The reason that there are different results in different places is based on local politics," Sharpton said to cheers from a group of about 200 supporters.

"When you have prosecutors that don't fear the police unions, that don't fear there's going to be some backlash, they go by the evidence. When you have prosecutors that are playing with politics they put the evidence aside, take four or five months to study it, they come back with nothing."

Protests in Baltimore Over Death of Freddie Gray

Garner died after being placed in an apparent chokehold by police last summer, but a grand jury on Staten Island cleared a white officer involved in the death.

Sharpton has complained the prosecutor who presented the case to the grand jury, Staten Island District Attorney Dan Donovan, was less than energetic. Donovan, who is running to fill an open seat in Congress, has said he presented the evidence fairly and impartially to the 23-citizen panel.

Sharpton noted Garner's death preceded nationwide protests over the deaths of Michael Brown in Ferguson, Missouri; Walter Scott, in North Charleston, South Carolina and most recently, Gray in Baltimore.

Sharpton also advocated for a federal law requiring cameras on all law enforcement officers, noting that video evidence proved critical in both the Charleston and Baltimore cases.

Gray's death from spinal injuries a week after his April 12 arrest provoked riots in Baltimore on Monday. The decision Friday to charge the officers with felonies ranging from assault to murder has brought celebrations to those same streets.

A lawyer for the police union has insisted the Baltimore officers did nothing wrong.

Sharpton also urged a vigorous voter registration campaign ahead of the 2016 presidential elections, adding that he wanted all candidates to explain their stand on police misconduct issues. He also noted that some of the officers charged in Baltimore were black.

"We need people that will stand for justice,'' he said. "We ain't for bad black cops."